1. Roberts, P. H. 1965 Proc. Roy. Soc. A283,550.
2. Schultz-Grunow, F. & Hein, H. 1956 Z. Flugwiss. 4,28.
3. Burkemlter, J. E. & Koschmieder, E. L. 1973 Submitted for publication.
4. Koschmieder, E. L. 1973 Adv. Chern. Phys., to appear.
5. Stuart, J. T. 1971 Ann. Rev. Fluid Mech. 3,347.